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Thread: Setting a transparency level of a picture issue

  1. #1
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    Default Setting a transparency level of a picture issue

    Hello,
    I have such method:
    private ImageIcon createSelectionPattern(int x, int y) {
    		BufferedImage bi = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration().createCompatibleImage(x, y, Transparency.BITMASK);
    		Graphics2D g2 = bi.createGraphics();
    		g2.setPaint(getFill());
    		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    		g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
    		int INS = x / 6;
    		g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.20f));
    		g2.fillRoundRect(0, 0, x, y, INS, INS);
    		g2.dispose();
    		return new ImageIcon(bi);
    	}
    The problem is with calling this method:
    g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.20f));
    I want to make this picture with 20% transparency, but with 0.2f I get 100% transparency. If I set it >=0.50f, I get 0% transparency, if <0.50f - 100% transparency. Why is it so?
    Last edited by Asido; August 28th, 2010 at 10:22 AM.


  2. #2
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    Default Re: Setting a transparency level of a picture issue

    Quote Originally Posted by Asido View Post
    Hello,
    I have such method:
    private ImageIcon createSelectionPattern(int x, int y) {
    		BufferedImage bi = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration().createCompatibleImage(x, y, Transparency.BITMASK);
    		Graphics2D g2 = bi.createGraphics();
    		g2.setPaint(getFill());
    		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    		g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
    		int INS = x / 6;
    		g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.20f));
    		g2.fillRoundRect(0, 0, x, y, INS, INS);
    		g2.dispose();
    		return new ImageIcon(bi);
    	}
    The problem is with calling this method:
    g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.20f));
    I want to make this picture with 20% transparency, but with 0.2f I get 100% transparency. If I set it >=0.50f, I get 0% transparency, if <0.50f - 100% transparency. Why is it so?
    Hi,

    setComposite() is used to blend the source color with the destination color.i.e., Source is the one on which u draw and destination is the one that u draw. i.e., Source is similar to drawing board and destination is similar to the picture that u draw over the board.

    AlphaComposite.getInstance(AlphaComposite.SRC_OVER ,0.20f) will perform the following action: Multiply the alpha value of the source with 0.20f and this is the alpha value of ur final image.
    So,check the alpha value of ur source!!

    AlphaComposite.SRC_OVER will work on the following logic:
    If ur source is opaque,then it replaces the destination whereas if ur source is transparent,then ur destination remains unchanged.

    If u have doubts, u can visit this site:
    Blending Colors with AlphaComposite (Java Foundation Classes)

    Hope this helps

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